A profiling stone for the above purpose has a cylindrical jacket surface facing, in the working position, the inner pipe surface, whereby the surface enclosed by the jacket surface comprises outer surface profiling suitable for the production of the inner pipe profiling. A plurality of roller bodies are arranged around the circumference of the pipe. The roller bodies press the pipe within a working range against the surface profiling of the profiling stone. For this purpose the roller bodies perform a revolving motion around the pipe while the pipe is being moved axially at the same time.
An apparatus for performing such a method is equipped with a draw nozzle and a drawing device for transporting the pipe in a drawing direction, whereby a drawing mandrel is provided for cooperation with the draw nozzle. The drawing mandrel is arranged coaxially and comprises a supporting mandrel. A profiling stone is arranged at the free end of the supporting mandrel. The apparatus further includes a roller head with roller bodies each of which is mounted for rotation about its own axis and all are mounted for rotation about an axis coaxial with the pipe to be worked.
A method and apparatus of the type mentioned above have become known through Japanese Patent Application No. 64-312046 published under No. 3-169421 (A). Such a method and the respective apparatus for performing the method have been found to be quite reliable. The substantially cylindrical profiling stones inside the pipe to be profiled perform their function satisfactorily. However, the production of such stones is quite expensive. For performing the method, the outer revolving roller bodies must make a pipe smaller, whereby the pipe is internally somewhat larger than the diameter of the profiling stone. For this purpose the rollers press the pipe against the profile of the profiling stone. This pressing takes place in a zone that is relatively short in the axial direction. This zone is substantially smaller than the length of the profiling stone. As a result, the press-on forces can be maintained relatively small, whereby simultaneously the specific forces can be sufficiently large. However, this feature has the consequence that in the relatively small working range of the roller bodies the profile of the profiling stone is rather quickly worn out so that the expensive profiling stone must soon be exchanged, although only a portion of its entire profile is worn out while the rest of the profile is still as good as new.